1. Field of the Invention
The present invention relates to a magnetic material that is employed as a high performance permanent magnet and a manufacturing method of the same, and a bonded magnet using the same.
2. Description of the Related Art
So far, as a kind of a high performance permanent magnet, a rare earth magnet such as a Sm--Co system magnet, a Nd--Fe--B system magnet or the like is known. In these magnets, a large amount of Fe and/or Co is included and contributes to an increase of saturation magnetization. In addition, rare earth elements such as Nd and Sm, due to the behavior of 4f electrons in a crystal field, renders a very large magnetocrystalline anisotropy. Thereby, an increase of coercive force is obtained.
Such a rare earth system high performance magnet is mainly used for electrical appliances such as a speaker, a motor, a measurement instrument or the like. Recently, demand for smaller size of various kinds of electrical appliances is high. Accordingly, a high performance permanent magnet is demanded to cope with this demand. For these demands, a Fe--R--N system magnet (R is one element selected from Y, Th and Lanthanoid elements)(cf. Japanese Patent Application KOKOKU Publication No. Hei 5-082041 and so on) is proposed. However, it does not necessarily have sufficient characteristics.
Further, Japanese Patent Application KOKAI Publication No. Hei 8-191006 discloses a R--Zr--Fe (Co)--N system magnetic material (R: rare earth element) in which a phase having a Th.sub.2 Ni.sub.17 crystal structure (hereinafter refers to as Th.sub.2 Ni.sub.17 crystal phase) is a principal phase. The Th.sub.2 Ni.sub.17 crystal phase, compared with a phase having a Th.sub.2 Zn.sub.17 crystal structure (Th.sub.2 Zn.sub.17 type crystal phase) can include a larger amount of Fe and/or Co. Accordingly, a magnetic material having the Th.sub.2 Ni.sub.17 crystal phase as its principal phase is expected as a promising forming material of a permanent magnet in which the saturation magnetization or the like is further improved.
However, the magnetic material, of which principal phase is the Th.sub.2 Ni.sub.17 crystal phase, obtained by the conventional manufacturing method has a disadvantage that its grain is relatively coarse. As a method for making fine grain, as disclosed in Japanese Patent Application KOKAI Publication No. Hei 8-191006, there are a rapid quenching method and a mechanical alloying method. However, these methods are disadvantageous from standpoints of improvement of manufacturing efficiency and reduction of manufacturing cost.
On the other hand, in the R--Fe--B system magnetic material, as a means for obtaining a fine grain, a HDDR (Hydrogenation-Disproportionation-Desorption-Recombination) method is known (cf. Japanese Patent Application KOKAI Publication No. Hei 1-132106). The HDDR method will be described in the following. In the case of the R--Fe--B system magnetic material, for instance, first, a R--Fe--B system mother alloy of which principal phase is R.sub.2 Fe.sub.14 B phase is heat treated in an atmosphere of hydrogen to transform into respective phases of RH.sub.X, Fe.sub.2 B, and Fe. Then, in a dehydrogenation process, H.sub.2 is removed from the material to form again the R.sub.2 Fe.sub.14 B phase. Thus obtained alloy has a recrystallization texture of which principal phase is a fine R.sub.2 Fe.sub.14 B phase of an average grain diameter of approximately 0.05 to 3 .mu.m. Thus, the HDDR method enables to obtain a fine texture only by an atmosphere treatment in an electric furnace, accordingly, from the standpoint of the manufacturing cost, is advantageous.
There are several reports in which the HDDR method is applied in magnetic material other than the R--Fe--B system. Mat.Chem.Phys.32, 280 to 285 (1992), for instance, discloses a Sm.sub.2 Fe.sub.17 N.sub.x system magnetic material of which principal phase is the Th.sub.2 Zn.sub.17 crystal phase and which is prepared by use of the HDDR method.
Further, Japanese Patent Application KOKAI Publication No. Hei 8-037122 discloses a manufacturing method of a magnetic material where, a R--M--T system alloy (R: rare earth element, M: metallic element such as Al, Ti, V, Cr or the like, T: Fe, Fe--Co) of which principal phase is the Th.sub.2 Zn.sub.17 crystal phase is first HDDR treated, thereafter, nitrogenized to prepare a R--M--T--N system magnetic material of which principal phase is the Th.sub.2 Zn.sub.17 crystal phase or a TbCu.sub.7 crystal phase. Further, in Japanese Patent Application KOKAI Publication No. Hei 4-260302, an alloy having a crystal structure of R.sub.2 (T,M)L.sub.17 system (R: rare earth element, T: Fe or Fe--Co, M: metallic element such as Zr, Hf, Nb, Ta or the like) is exposed to the HDDR treatment.
All the HDDR treatments disclosed in these Patent Publications are given to the alloys of which principal phases are the Th.sub.2 Zn.sub.17 crystal phase. Further, in Japanese Patent Application KOKAI Publication No. Hei 8-037122, an anisotropic magnetic material is obtained. Incidentally, in Japanese Patent Application KOKAI Publication No. Hei 4-260302, in order to invest an anisotropy to a magnetic material, the M element is added, and the crystal structure of the magnetic material is described as the R.sub.2 (T,M).sub.17 type. In the absence of the M, the crystal structure is the Th.sub.2 Zn.sub.17 type, also in the presence of the M, similarly the crystal structure is considered to be the Th.sub.2 Zn.sub.17 type.
Thus, though the HDDR method is known as a technique for making fine grain of the magnetic material, there is no disclosure in which the HDDR method is applied to the magnetic material that contains the Th.sub.2 Ni.sub.17 type crystal phase as an indispensable component.